Our goal is to characterize measles virus antigens and other components expressed on the surface of infected cells which are the targets of the immune response. Monoclonal antibodies against the five structural proteins of measles virus have been produced and are used to characterize and purify these viral components. Three components, the hemagglutinin (HA), the fusion (F), and the matrix (M) proteins are incorporated into the membrane. The nucleocapsid associated protein (N) and the phosphoprotein (P) are internal components. Each of the virus proteins has unique function and immunological properties. The cellular immune responses to epitopes on each of the five proteins are being assessed by lymphocyte proliferation and cytotoxicity. Measles virus infection can be complicated by persistent infection of the nervous system and although most of the research is being conducted with the Edmonston strain, the hamster neurotropic strain (HNT) which is neurovirulent and characteristically produces CNS infections in experimental animals is also being studied. The biological, immunological, and molecular properties of Edmonston and HNT strains are being compared. Relationships between human MHC molecules and the measles antigens are being examined.